The present invention is directed, in general, to wireless communication and, more specifically, to a transcoding system and method that optimizes documents to be transmitted to a mobile station for display thereon and a wireless infrastructure employing the same.
The importance of wireless communication systems today is evident by its usage in popular platforms such as mobile telephony, paging systems and portable computers. The popularity of wireless communication systems is, in part, a result of the flexibility the system provides to the user. The user is provided instant communication on demand at any location, within certain restrictions. While conventional wireless communication systems provide both voice communication and document transmitting capabilities, the next generation systems will provide enhanced communication services such as electronic mail and full multimedia communication. The expanded capabilities will further enhance the user document accessing and retrieval capabilities.
With regard to the document handling capabilities, documents are stored in various formats depending on the creator, the maintainer or distributor of the document. Mobile stations (especially wireless stations), however, are generally unable to interpret all formats. Due to the compactness and relative simplicity of the design, the mobile stations are not equipped with the hardware or computational power to accommodate multi-format document interpretation. Thus, the mobile stations only recognize a limited number of document formats thereby effectively limiting the document handling capability thereof.
Another problem encountered when transmitting information to mobile stations is the relatively low communication bandwidth associated with the mobile station. Documents in formats that are not supported by the mobile station (e.g., documents that include both text and graphics to a station that supports text-only documents) may require additional bandwidth. Obviously, the use of the excess bandwidth is an inefficient use of bandwidth if the mobile station is unable to recognize a substantial portion of the document. As the congestion in the wireless communication systems continues to increase, the multi-formatted documents will place undue burdens on the available bandwidth of the system (if the station cannot recognize the document) thereby resulting in a slower overall system response time.
With regard to the content of the documents, the document may be formatted for certain graphics display systems such as video graphics array (xe2x80x9cVGAxe2x80x9d) or super video graphics array (xe2x80x9cSVGAxe2x80x9d). If the mobile station has graphics capability, the screens associated therewith tend to be very small and monochrome. For instance, a VGA system in text mode provides a resolution of about 720 by 400 pixels; in the graphics mode, the resolution of the VGA system is about 640 by 480 pixels (with 16 colors) or 320 by 200 pixels(with 256 colors). The display for a mobile station (such as a pager) only provides a resolution of about 80 by 25 pixels. Thus, transmitting data to a station without considering the station""s display capabilities and screen resolution is an inefficient use of the limited bandwidth available for the wireless communication systems.
Currently, documents are transmitted in wireless communication systems without regard to the capabilities of the mobile stations. Thus, to recognize and, if possible, process documents in different formats, the mobile station must be equipped with additional hardware and software to perform the necessary tasks. As a result, the mobile station expends more energy in an attempt to process the document. Mobile stations such as portable computers and mobile telephones are generally powered by a plurality of batteries. Obviously, the operational life of the mobile station depends on the operational life of the batteries powering the system. The operational life of the batteries is a function of its stored energy capacity and the power requirements of the device supported by the batteries. A lower stored energy capacity results in a shorter operational life-span. Similarly, the greater operational demands of the supported device reduces the operational life of the battery. When a mobile station uses more hardware and software, the power requirements necessary to adequately power and operate the mobile station are increased. Therefore, it is desirable to reduce the demands of the mobile station to ultimately reduce the demands on the power system (e.g., battery system).
Therefore, what is needed in the art is a recognition that mobile stations have varying degrees of document handling capabilities and, in conjunction therewith, a system and method of transmitting documents to a mobile station in a format that corresponds to the document handling capabilities and, in particular, the document display capabilities thereof.
To address the above-discussed deficiencies of the prior art, the present invention provides a system and method for transcoding a document to be transmitted to a mobile station according to document display capabilities thereof and a wireless infrastructure containing the same. The system includes: (1) a station identifying circuit that receives data indicating a particular mobile station""s document display capabilities and (2) a transcoding circuit that modifies the document according to the document display capabilities before the document is transmitted to the particular mobile station, the particular mobile station thereby freed of having locally to substantially modify the document according to the document display capabilities.
xe2x80x9cTranscodingxe2x80x9d is defined for purposes of the present invention as a process of translation, transformation, modification or substitution that results in a document being changed in terms of its structure, format, length, attributes (to be defined) or temporal transmission order. xe2x80x9cDocumentxe2x80x9d is defined for purposes of the present invention as anything that can be visually displayed (such as text, a graphical image, a photograph or a video stream) and any data ancillary to that which is visually displayed (usually in the form of multimedia attachments, such as imbedded images or sounds). Those skilled in the art are aware that today""s multimedia systems operate on integrated multimedia documents. The present invention is fully capable of transcoding such documents, as well as more conventional, single media documents.
The present invention therefore introduces the broad concept of modifying documents to accommodate features or limitations of the mobile stations to which they are to be transmitted before they are actually transmitted. When the documents arrive at the mobile station, they are ready to display, without requiring substantial modification. Not only does the present invention relieve the mobile station""s processor of the overhead of performing such modifications, the mobile station is not required to contain the software or circuitry required to perform the modifications. The result is twofold: mobile station power is saved (allowing longer battery life) and, in cases wherein modification results in a reduction in document size, bandwidth and the time taken to transmit the document are decreased (allowing a given infrastructure to communicate more documents).
In one embodiment of the present invention, the transcoding circuit translates the document from a first display format to a second display format, the document display capabilities including a capability of displaying the document in the second display format. Today""s common still image formats include: bitmap (xe2x80x9cBMPxe2x80x9d), Graphics Interchange Format (xe2x80x9cGIFxe2x80x9d), Joint Photographic Experts Group (xe2x80x9cJPEGxe2x80x9d) and Tagged Image File Format (xe2x80x9cTIFFxe2x80x9d). Today""s common video formats include: Motion Picture Experts Group (xe2x80x9cMPEGxe2x80x9d) I and II and IEEE H.320. Thus, the particular mobile station may be capable of displaying a JPEG-encoded document, but not one that is GIF-encoded. Thus, the station identifying circuit determines this capability (or limitation, as the case may be); and the transcoding circuit responds by automatically transcoding GIF-encoded documents into JPEG-encoded documents. Alternatively or additionally, the transcoding circuit may scale, skew, rotate, change the aspect ratio of, or otherwise warp the document to fit the mobile station""s display.
In one embodiment of the present invention, the transcoding circuit translates the document from a graphics-based format to a text-based format, the document display capabilities including only a capability of displaying the text-based format. Some mobile stations may only be text-capable. In such cases, the transcoding circuit may contain text recognition algorithms or circuitry to transcode those portions of a graphical document that contain text into the text-based equivalent. Alternatively, some mobile stations may not have character-generating capability. In such cases, the transcoding circuit transcodes text-based documents into a graphical document.
In one embodiment of the present invention, the transcoding circuit rearranges a temporal order of transmission of the document to the particular mobile station. For example, the document may contain text with embedded graphical images or sounds. Since text requires less bandwidth to transmit than graphical images or sounds, the transcoding circuit may reorder the document to have the text to be transmitted first, followed by the graphical images or sound. In this way, the user first sees the text, and is not required to wait until the ancillary data are transmitted.
In one embodiment of the present invention, the transcoding circuit modifies an attribute of the document. xe2x80x9cAttributexe2x80x9d is defined for purposes of the present invention as a characteristic of the document, such as the color (or absence thereof) or the resolution of the document. If the station identifying circuit identifies the mobile station as not having color display capability, the transcoding circuit can remove the color from documents before they are transmitted to the station. If the station identifying circuit identifies the mobile station as having a low-resolution display, the document can be so-modified.
In one embodiment of the present invention, the transcoding circuit divides the document into pages. The page size and shape are preferably a function of the characteristics of the mobile station display. Such division allows a user to page through the document, even though the document, in its original format, may not have been structured to allow paging.
In one embodiment of the present invention, the document contains control codes, the transcoding circuit modifying the document according to the control codes. Therefore, documents may anticipate that they will require transcoding and include codes (such as optional page breaks) that make the transcoding process more effective or efficient. Widely-disseminated documents may benefit most from such control codes.
In one embodiment of the present invention, the station identifying circuit and the transcoding circuit are embodied in a sequence of software instructions executable in a computer system associated with a base station. Alternatively, the station identifying circuit and the transcoding circuit may be embodied in hardware or firmware and may be present in the base station itself.
In one embodiment of the present invention, the station identifying circuit receives the data from a database of predetermined document display capabilities. Thus, rather than determining the document display capabilities dynamically, the present invention may operate with a database of stored (perhaps previously-determined) capabilities.
In one embodiment of the present invention, the document display capabilities are user-determined. Thus, the user of the mobile station may select a subset of the station""s true capabilities, perhaps for economic reasons.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.